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50 Billion Suns! -The Biggest Single Object in the Universe [attachment=7476]Scientists have determined the mass of the largest things that could possibly exist in our universe. New results have placed an upper limit on the current size of black holes - and at fifty billion suns it's pretty damn big. That's a hundred thousand tredagrams, and you'll never get the chance to use that word in relation to anything else.Black holes are regions of space where matter is so dense that regular physics just breaks down. You might think physical laws are immutable - you can't get out of gravitational attraction the same way you can get out of a speeding ticket - but beyond a certain level laws which determine how matter is regulated are simply overloaded and material is crushed down into something that's less an object and more a region of altered space.While there's theoretically no upper limit on how big a black hole can be, there are hard limits on how big they could have become by now. The universe has only existed for a finite amount of time, and even the most voracious black hole can only suck in matter at a certain rate. The bigger the black hole, the bigger the gravitational field and the faster it can pull in matter - but that same huge gravitational gradient means that the same matter can release huge amounts of radiation as it falls, blasting other matter further away.Based on this self-regulating maximum rate, scientists at the Harvard-Smithsonian Center for Astrophysics, Massachusetts, and the European Southern Observatory, Chile, have calculated an upper limit for these mega-mammoth masses. Fifty billion suns, that's 100 000 000 000 000 000 000 000 000 000 000 000 000 000 kg, otherwise known as "ridiculously stupidly big" and triple the size of the largest observed black hole, OJ 287.There are potential problems with this calculation. Based as it is on the radiation outflow from a black hole, new discoveries could change this estimate - though only from "insanely massive" to "ridiculously ginormous."Source: the Daily Galaxy
Quote from: yor_on on 24/03/2009 21:29:18I may have got it all backwards then?Sorry LeeE, I got the impression that you said that the in-falling observer wouldn't get past that EV? But here you seem to say exactly the same as I think too "from their point of view, they will seem to be running at 'normal' time " and so they will, as seen from their frame of reference, just keep falling in. What I reacted on was the statement that "t = 0" at the eventhorizon. How exactly do you see that idea? Yes, they'll think that time is running normally for them, but at the point where t0 = 0, they'll stop thinking; their rate of thinking will slow and stop, so they won't be aware that they've stopped thinking...........I think this just actually complicates the issue though. The actual reason that I think they couldn't reach the event horizon is that it may be infinitely far away in spatial terms, regardless of how time-dilation effects the relative energy that's seen to be expended, say by a battery powered light inside the craft, by both the local and distant observers. .......
I may have got it all backwards then?Sorry LeeE, I got the impression that you said that the in-falling observer wouldn't get past that EV? But here you seem to say exactly the same as I think too "from their point of view, they will seem to be running at 'normal' time " and so they will, as seen from their frame of reference, just keep falling in. What I reacted on was the statement that "t = 0" at the eventhorizon. How exactly do you see that idea?
You mean that by calculating the gravitational force between the sun and Earth we will find out how fast it would take us in time to get to, let's say, our closest BH?I'm not sure how you think here. So, I'll guess if that's ok with you:)
Are you looking at gravity as a 'propagating force'?And wondering of how big a black hole would need to be to have the same 'gravitational force' relative Earth, and perhaps if it then would take the same approximate time, as seen from the frame of someone traveling, to get from Earth to that BH (black hole).
So when you calculate that 'gravitational force' you are in fact looking on how 'space wrinkles'. To have a black hole or a quasar that strong would be quite a feat, and we would all 'fall' into it. We are in fact traveling towards something called the "Great Attractor" at a breakneck speed of 22 million kilometers (14 million miles) per hour. That's our Milky Way traveling btw with tens of thousands of other galaxies too. http://en.wikipedia.org/wiki/Great_AttractorIf it is this you were thinking of:)
I'm not familiar with Gullstrand-Painlev coordinate systems - interesting name though - but as there's an absolute difference in the elapsed durations if the clocks are reconciled when the traveling clock returns to the same reference-frame as the observer, I can't see it making much difference because whatever coordinate system they're in, it will apply to both but won't cancel the difference.I might have misunderstood you there though.
accelerating system or a uniformly moving system.
Serious readers of this forum may want to consider:1. Evidence from Case Western Reserve University [Science (21 June 2007)] that Black Holes do not exist:
What would that be in elephants or blue whales, the normal units for awfully big things?